1. Field of the Invention
The invention relates to a sewing thread comprising a thread, and a precursor material impregnated into at least the outer surface of the thread, the precursor material capable of being activated after processing of said sewing thread to a product which imparts an increased adherence between the sewing thread and a stitched material in a stitched connection produced with such a thread, a sewable area structure sewn therewith, and a method for obtaining at least splash-proof stitched connections.
2. Description of the Related Art
One essential quality feature of textile stitched connections resides in the way the sewing thread material is locked in the material of the sewable area structure to be attached by means of the stitched connection. In lockstitching, such locking is achieved continuously with each stitch, with the underthread provided on a spool of small capacity locking the upper thread. In chain stitching, merely threads paid out by one or several cones of large capacity are used without being locked in every stitch. Locking the thread in chain stitching is achieved by nothing else but sewing across the ends of the stitched connection. If the stitched connection is damaged at a location between its ends, one pull at the thread consequently causes the entire connection to come undone. For this reason, the use of chain stitching is very limited or disadvantageous under practical conditions where a coming undone of stitched connections is accepted due to a lack of alternatives.
For the rest, lockstitched connections, being of higher quality, require considerable work effort as they do not lend themselves to automation. Once the available underthread on a spool has been used up, spool changes must be carried out manually, such that the sewing procedure has to be interrupted repeatedly, even in terms of several minutes under given circumstances, in order to permit a spool change. If it were possible to use a chain-stitched connection, work could be continued uninterruptedly throughout a whole work day or even longer, such that various automation measures might find application.
Due to the fact that its outer surface may be provided with an increased adhesiveness or adhesive effect after sewing, an adhering of the thread to the stitch linkage and to the textile or material to be sewn results in the area of the needle holes. Hereby the thread is held to each stitch linkage in a manner which is similar to the lockstitch thread being immobilized by the underthread. The resulting security against coming loose of the chain-stitched connection is essentially the same as in the case of a lockstitched connection. The essentially more favorable manufacturing option of the chain-stitched connection may thus also be made use of in cases hitherto requiring lockstitching in order to prevent the connection from coming undone. At the same time, further advantages of chain stitches, such as a higher elasticity in comparison with lockstitches, may be made use of. On the other hand, however, a sewing thread according to the invention may also be utilized for lockstitching if required, e.g. for reasons of looks, wearing comfort, or the like.
As a rule, the increased adhesive effect may most advantageously be achieved by a bonding effect. This allows to attain very high adhesive forces, guaranteeing a durable attachment of threads to the stitch linkages and inside the needle holes.
Furthermore it is known to seal textile stitched connections by covering the stitched connections with adhesive or welting ribbons. This, however, requires a considerable additional expense. Without the use of such additional sealing means, a flaw is in any case created when the thread passes through the needle hole.
DE-A-40 25 291, moreover, discloses a method for producing water or moisture proof stitched connections in sewing woven synthetic or rubber materials, or woven materials coated with synthetic or rubber, or multiple-layer synthetic or rubber materials, which in a given case are reinforced with metal foil, by inserting a body core of synthetic or rubber foil between the parts to be sewn upon sewing and by causing the sealant emanating from the pierced body core to cross-link. In particular, organo-polysiloxane masses are used as sealants.
Such a method, however, has the disadvantage that on the one hand, the needle constantly contacts a sealant capable of curing, thereby affecting the precision of the stitched connection over longer sewing periods, and on the other hand results in residues of sealant material on the needle which, upon continued sewing, may cause damage inside the fabric and/or to the needle, or even to the sewing device.
Moreover the method of DE-A-40 25 291 requires more precise positioning of the sealant-filled body cores, particularly hoses, bringing about considerable problems of positioning and corresponding technical expense if stitched connections under given circumstances are several meters in length.
One further disadvantage of this prior art method is founded in the fact that sealant constantly leaks at the needle holes, further favored by the circumstance of the articles to be sewn, as a rule, being positioned between the pressure leg and the bottom feeder, whereby additional pressure is exerted on the tube and its content of sealant, thus causing the sealant to constantly emanate and frequently reach locations of the sewing device and of the article being sewn where the sealant is not welcome or even harmful.
Consequently there is a need to particularly form textile stitched connections between fluid-proof textile materials by means of textile stitched connections which also fulfil the corresponding sealing requirements without essentially expensive additional measures. In such a case, the textile material may often replace synthetic sheets which are sealingly connected to each other by fusing.